Strange behaviour when recording Physics to IPO...

I’ve made a chain of boxes linked together with rigid body joints…

As I am lazy, I duplicated two boxes to make the other elements of the chain.

OOOOOOOOO <— my chain yeah…

Launched a simulation and my little chain goes as predicted…

Ok. Nice. Now I want to export the ipo to use out of the Game Engine.

The simulation run smoothly.

But when I exit the game engine, #BAM# some of the elements have changed their initial position at frame 1… They are superimposed to their parents (and sometime the parents are superimposed to their duplicate)

OOO------OO <— my chain after IPO record… gaaah!

:frowning: Can somebody tell me how I can avoid that? Or if it it an icky bug I should report?

Did you add them all in the same view (check axis orientations) and did you Ctrl-A them all?


From what you are describing, it sounds like some of the objects are sharing IPO’s, probably a result of the duplication. This would especially be the case if the object already had an IPO assigned to it before you did the duplicating (even if it was a blank IPO).

I would recommend that you assign a separate, blank IPO to each object in the chain before running the simulation. No guarantees, but I’m pretty sure that should do the trick.

Let me know.


Did you add them all in the same view (check axis orientations) and did you Ctrl-A them all?
As I said, I duplicated them from one object. So basicaly they are all oriented the same way. And I purposefully wanted their orientation to match the rigid body joint constraint (I want an horizontal chain with X axis pointing up)

Tried. But it didn’t work.

When you record game physics, it wipes all the previous IPOs. So assigning a “0” key isn’t of much use.

It looks more like it is keeping the joints info from previous state or something…

The only solution I have found so far, is to completely finish your physic object before doing anything animation related. Once you have IPO keys, you are pretty much f***ed up if you need to add something… Even when you erase all the IPO keys before launching the GE again… That’s what I found strange… :frowning: